To meet requirements of downsizing and weight saving and high functionality of electronic equipment, downsizing, reduction in thickness and reduction in pitch of semiconductor packages are rapidly in progress. Further, with respect to their mounting method, surface mounting suitable for high density mounting on a printed board or the like is dominant. As the semiconductor packages and their mounting methods are in progress, improvement in reliability of a sealing material for semiconductors in high temperature environment is more highly required.
Particularly for automobiles, mounting of controlling members and electronic equipment which heavily employ semiconductors is in progress. Accordingly, a sealing material for semiconductors is required to have flame retardancy imparted without using a flame retardant with a heavy environmental burden, to be resistant to mechanical external pressure such as vibration and acceleration, and to be guaranteed to operate in severe high temperature environment in the car. Thus, the sealing material is required to have high temperature storage life (hereinafter sometimes referred to as HTSL properties) and high temperature operating life (hereinafter sometimes referred to as HTOL properties) higher than those required for general equipment.
In order to meet such requirements, a means of improving high temperature life has been employed by reducing ionic impurities and electrically conductive impurities in a sealing material for semiconductors as far as possible, by incorporating an amorphous silica powder at a high density to reduce moisture absorptivity, by adding an ion trapping agent, or by employing a resin containing no flame retardant such as halogen, antimony or inorganic phosphorus (Patent Documents 1 and 2). However, by such a means, the effect of improving the high temperature life is still insufficient, and a sealing material for semiconductors which satisfies severe requirements of HTSL properties and HTOL properties has not yet been known.    Patent Document 1: JP-A-2000-230111    Patent Document 1: JP-A-2004-035781